Coded track circuit signaling system



May 1, 1951 N. D. PRESTON CODED TRACK CIRCUIT SIGNALING SYSTEM FiledMarch 6, 19 47 3nnentor Patented May 1, 1951 Neil D'. Preston,Rochester',jN. Y.) as'si'g'no'r-to' General Railway Signal Company;Rochester,

Application March e,194'z, serialnmszflcs (claus -34 2 Claims;-

The presentinvention relates to block signallin'g systems on railroadsusing "coded track circuits, and more' particularly pertains tothe-improvement of the code receiving apparatus em p'loy'ed'in suchsignalling systems.

The various blocks of a signalling system employing coded track circuitsusually comprise a single track circuit for each bl'ock,-eachjtrackcircuitbeing provided with suitable code transmitting'apparatus at oneend of'thetrack circuit and suitablecode responsive means at the otherend of "the track" circuit; The code'transmitting In such a system,as-abovebriefiy' mentioned, a

code followingtrackrelay is' usually provided with contacts forgoverning the code receivingapparatus, and it is desirable to haveaminimum number of contactson this relay in order to have the'relay' assensitive as possible to th'e cod'e pulses of the associated-trackcircuiti These contacts' on -th'e-code following track relay incontrolling the decoding apparatus may under certainadverseconditions-become misplaced; or fused'and it is desirable tohave thedecoding apparatus so organized that under such circumstances any*failure'is'on the side "of safety.

Generally speaking and withoutattempting to define the exact nature andscope of the present invention; it is proposed to providetwo slowactingrelays; one of which is energized when the code following trackrelayisupicked up,and" the other of which is energized when thecode-following trackrelayis released providing-the other slowactingrelayis then picked up. If these two relays were provided in 1this particular relationship without further modification, it mightha'ppen-'5 ifthecontacts of the code :followingJ-track relay" shouldbecome misplaced orfused together orthelike, that both of the slowacting relays would become steadily energized even-though the codefollowing track relay had ceased its "operation." Thiswould give anerroneous: signal indicatio'ni However, the present invention providesthat I the" slow acting repeater relay i governed in accordance withtheop'erated condition of the code front contact repeating relay' whichmust be pickedup in order'ior sjuch' slow acting relay to be energized;and in addition;- the controlfor the slow acting back con-tact repeatingrelay includes aback contact of the} quick acting repeater relay.In'this'way, the quick actingrepeater relay-must respond *tocodingoperation of the code following track relay in -'order-topick-up-either of the slow acting repeater relays'. lf -the contactsbecome fused or misplaced with this organization, the-most that canhappen is --tliat=thequick acting repeater relay and the slow actingfront contact repeater relay maylee" picked up steadily, but under sucha condition theslow acting back contact repeater relay can noticeenergized due to the picked 'upcond-ition of the quick acting" repeaterrelay 7 lt is a further'object-of the invention to provide that th'edecoding apparatus which is distinctively responsive to the-differentcode rates shall be governed -fromcontacts of the quick acting repeaterrelay so'as to minimize the number of contacts on' the code followingtrack relay andalso to prevent-operation of the decoding means if 1 thecode following track relay ceases operation.

Other objects; purposes-and" characteristic f eatu res of the presentinvention will be in part obvious from the accompanying drawingsyand inpart pointed out as the-description progresses.

In-desoiribin'g the invention inxdetail, reference will be made to theaccompanying drawing; in which 'thoseparts having similar features andfunctions are" designated by like letter" reference characters which aregen'erally'made distinctive by reason of distinctivepreceding' numeralsrepresentative of theirlocation or association with other devices havingreference characters with like numerals, and" in whi'ch't The singlefigure of theld'rawing illustrates one section of a codedtrack"circuitsignalling'jsysmore with the pur'pb'se of' making it easyto uriderstand the": principles an'd mo'de of operation than withmesses-or illustrating the specific construction and arrangement ofp'arts" that wqulube empioyeci iii-practice; Thusftlie 'val'io'iisrelays and theircontactsare illustratedin a; conventional manner, andsymbols are used to indicate the connection of terminals to batteries orother suitable sources of electric current instead of showing all of thewire connections to these terminals.

The symbols and are employed to indicate the positive and negativeterminals respectively of suitable batteries or other sources of directcurrent; and the circuits with which these symbols are employed areassumed to always have current flowing in the same direction, althoughit is to be understood that in some cases alternating current might besubstituted for the direct current, and in such cases the and are to beused as indicating the relative instantaneous polarities of thealternating current.

With reference to the single figure of the drawing, a stretch of trackhas been shown divided into track sections by suitable insulated jointsof which the track section 2T has been shown completely and the tracksections IT and 31 in part only. Color light type signals 2 and S-areshown at the entrance ends of the track sections 2T and ST respectively,assuming a normal direction of traffic from left to right as indicatedby the trafflc direction arrow. These signals can of course be of anysuitable type desired.

At the exit end of each track section (such as section 2T) suitable codetransmitting apparatus is located to transmit driven codes of differentdistinctive rates in accordance with traffic conditions in advance asgoverned by the code receiving means for the entrance end of the nextadjoining track section.

At the entrance end of each track section (such as section 2T), asuitable decoding apparatus is located for receiving the differentdriven codes and decoding them so as to properly control the associatedsignal (such as color light signal 2).

Although this typical track section might in some cases have codetransmitting and receiving apparatus for inverse codes, such apparatushas not been shown for the sake of simplicity in the illustration, butit should be understood that the decoding apparatus illustrated asemployed in connection with driven codes may also be employed inconnection with the decoding of inverse codes.

As typical of all such track sections above briefly described, referencemay be made to the track section 2T in which coding contacts ISGC and15C are illustrated as associated with the signal location 3. Forconvenience it is assumed that these contacts will continuously operate,and when the decoding relay, conveniently termed slow acting backcontact repeating relay 3B? and governed in accordance with the codes intrack section ST, is picked up closing front contact l4, a code of theI80 code rate is applied to the track section 2T with the energy forsuch pulses being supplied from the battery B. When the relay 3BP isdeenergized closing its back contact Id, code pulses of the 15 code rateare applied to the track section 2T from the battery B. It is to beunderstood that the relay 3BP is picked up whenever a code is receivedover the track section 3T, but is deenergized whenever the track section3T is occupied by a train or the reception of code ceases for some otherreason. The usual clear and caution code rates .of 75 and 180 pulses perminute have been selected for the coders 15C and I880 for the purposesof this disclosure, but it should be understood that other suitable coderates might be employed if desired. Also, this simplified illustrationof the application of different codes is employed merely for thepurposes of simplifying the present disclosure, it being understood thatvarious organizations for transmitting code pulses of different coderates may be employed as desired.

At the entering end of the track section 2'1, and associated with thesignal 2, is a track relay ZTR which is connected across the track railsof the track section so as to follow the code pulses transmitted overthe rails. This relay 2TR picks up its contact 23 for each code pulseand releases its contact 23 between successive code pulses. This codefollowing track relay 2TB, may be of the neutral type as assumed for thepurposes of this disclosure, or it may be of the polarized type, thatis, its contacts may be biased to one position by gravity or suitableresilient means, and operated to a picked up or actuated position inresponse to energization by only a particular polarity.

A quick acting repeater relay ZTP is provided with an energizing circuitincluding a front contact 23 of the code following track relay 2TB. Alsoa slow acting front contact repeating relay ZFP is provided with anobvious energizing circuit including the front contact of the quickacting repeater relay Z'IP.

A slow acting back contact repeating relay ZBP is provided with anenergizing circuit closed from and including back contact 23 of the'code following track relay 2TB, back contact 5 of quick acting repeaterrelay ZTP, front contact 6 of slow acting front contact repeater relay2FP, and windings of relay 2BP, to

With this organization, it can be seen that each time the code followingtrack relay is initiated into operation for any particular code rate, itwill close its front contact 23 on the first code pulse which will berepeated by the quick acting repeater relay 2TP, and the closure of itsfront contact l will energize the front contact repeater relay ZFP. Ifthe slow acting front contact repeater relay ZFP is too slow acting tobe picked up on its first energization, it will pick up on somesubsequent energization such as the second or third, and after it hasonce been picked up, it will remain picked up between successive codepulses.

As soon as the front contact repeating relay ZFP has picked up andclosed its front contact 6,

the next following deenergization of the code following track relay 2TBwill close its back contact 23 followed by the closure of back contact 5so that the relay ZBP will be energized for that space between twosuccessive code pulses. If the relay 2BP does not pick up on the firstsuch energization, it will upon a subsequent energization such as thesecond or third.

Once the relays ZFP and ZBP have both been picked up in response to thereception of a code, they remain picked up so long as that code rate orany other code rate is continuously received; but if the operation ofthe code following track relay 2TB. ceases, these relays willsuccessively drop awayin accordance with their slow releasingcharacteristics. 7

Under conditionsof no code in the track section ET, the relays 2FP and2BP are both dropped away closing back contact [2, so that the red lampR, of signal 2 is energized causing such signal to. display a stopindication. On the other hand, when the relay ZBP is picked up duringthe reception of a code, regardless of its particular rate, the frontcontact I2 is closed so that the yellow or green lamps of signal 2 areener- -open condition of back contact 5.

gized depending upon the particular rate of the code being received.This is determined bysuitrepeater relay 2TP is operated to its oppositepositions. The secondary winding of the transformer 8 is connected tothe primary of the transformer I0 through a condenser 9 in such a manneras to be tuned for the 180 code rate but to pass substantially no energyor a very small amount of energy in response to the 75 code rate. Thisenergy induced in the secondary of the transformer 8 and caused to flowin the tuned circuit including the primary of the transformer Ill, issupplied through the secondary of the transformer In through a suitablerectifier II to convert the alternating current to direct current whichis supplied to the slow acting distant relay 2D.

In brief, the relay 2D is caused to pick up only when the code receivedby the code following track relay ZTR and repeated by its quick actingrepeater relay ZTP is of the 180 code rate. It should of course beunderstood that other code rates might be employed either separately orin addition to the ones shown, and that decoding means distinctivelytuned for these other rates may be employed as desired for additionalsignal indications.

In the particular embodiment of the invention, the reception of a 75code rate means that the relay 2D is released so that the yellow signalY is energized through front contact l2 and back contact I3; but thereception of a 180 code rate results in the energization of the relay2]) so that the green signal G is energized through front contacts l2and I3.

While the section 2T is occupied by a train it will be apparent that nocode will be repeated by the code following track relay 2TB because thetrack rails are shunted. But when the train passes into the tracksection 3T and out of the track section 2T, the relay 3BP is deenergizedand a 75 code rate is applied to the track section 2T and to the relay2TH. When the train passes from the track section 3T into the tracksection 4T (not shown), then a 75 code rate will beapplied to the tracksection 3T causing the relay 3BP to be picked up so that a 180 code isapplied to the track section 2T.

Although the apparatus employed with coded track circuits for signallingsystems is usually very reliable, and will operate over long periods oftime without failure, it may happen that a static charge or some othercondition may occur such that the front and back points of the contact23 become fused. In such a circumstance, the relay 2T? would be steadilyenergized, and in turn would cause the steady energization of the relay2FP. However, even though energy is supplied through the back point ofcontact 23, this energy cannot energize the relay 2BP because of theThus, it is obvious that such a failure does not result in the erroneouscontrol of the signal but rather causes such signal to indicate dangeror stop regardless of whether a code is being received or not.

Should it happen that the circuit for the relay ZTP fails to close, thenit is apparent that the relay ZFP would not be energized and thecontinued open condition of front contact 6 would likewise cause theslow acting back contact ZBP to be steadily deenergized. It can be seenthat under such a condition the signal 2 would be held 6 at Stop for tworeasons, i. e.,-the relay 25BPrwo111d be deenergized closing backcontactlL and Ethe failure of oper-ation of contact 1 to a 180 codewould cause the relay 2D to be deenergized. For these reasons, it isbelieved that the present inuention provides -a reliable (and safedecoding organization for codes used in ,acodedtrackcircuit signallingsystem.

Having described one form of coded track circuit block signalling systememploying novel decoding apparatus to give a safe and reliable decodingorganization as one embodiment of the present invention, it is desiredto be understood that the invention is shown in this connection for thepurpose of facilitating its disclosure, and that it can be applied tosystems of various other types; and it is to be further understood thatother specific embodiments and modifications of the invention may bemade, and that various adaptations and alterations may be required tomeet the problems of practice without in any manner departing from thespirit or scope of the present invention.

What I claim is:

1. In a decoding organization for checking the opening and closing ofthe contacts of a code following relay, a quick acting relay energizedeach time the code following relay is operated to one position anddeenergized each time it is operated to its opposite position, a slowacting repeater relay energized each time said quick acting relay isenergized only after its contacts have been picked up, said repeaterrelay being sufficiently slow acting to maintain its contacts picked upif said quick acting relay is energized and deenergized at relativelyfrequent intervals, and another slow acting relay energized each timethe code following relay is operated to its said opposite position onlyproviding said quick acting relay is deenergized with its contactsreleased and. said slow acting repeater relay has its contacts pickedup, whereby the cessation .of the operation of said quick acting relayeither because of the cessation of the operation of said code followingrelay or the failure of its contacts to open and close results in thecontinued deenergization of said another slow acting relay.

2. In a coded track circuit signalling system, a section of track havingcoded pulses applied thereto at different code rates dependent upontraffic conditions, a signal for governing trafiic over said section, acode following track relay adjacent said signal and responsive to thecode pulses in said section, a quick acting repeater relay for said codefollowing relay, a slow acting signal repeater relay for said quickacting relay, a slow acting control relay controlled through a frontcontact of said slow acting repeater relay and back contacts of saidcode following track relay and said quick acting repeater relay, wherebysaid signal control relay is energized whenever said code followingtrack relay is responsive to different codes but is deenergized wheneversaid code following track relay ceases operation, other signal controlmeans governed by the operation of said quick acting repeater relay onlyin response to a particular one of said different code rates, andcircuit control means for said signal governed by said slow actingsignal control relay and said other signal control means so as to governsaid signal distinctively in accordance with the different codes and toclear said signal only providing said quick acting repeater relay isactually following the response of said code 7 following track relay tothe difierent codes on UNITED STATES PATENTS said track section. 7Number Name Date NEIL PRESTON; 2,353,930 Rees July 18, 1944 7 2,366,988Rees Jan. 9, 1945 REFERENCES CITED 5 2,465,794 Fereday Mar, 29, 1949 Thefollowing references are of record in the file of this patent:

